Generator Forced Excitation Emergency Control (GFEEC) combined with a high excitation system ceiling voltage can make the best use of the generator strong excitation function and then improve the transient stability of the power grid. The generator excitation system is usually designed according to a uniform standard, such that it is impossible to consider the different adjustment performance that a unit can perform under actual faults. If differentiated control strategies or configuration of control parameters are applied to the generators after taking into account the adjustment performance difference, the coordination between power grid and source can be effectively optimized. In this paper, an optimized method of configuring the excitation system ceiling voltages of different generators is proposed. The sensitivity of the system transient stability margin index to the excitation system ceiling voltage of each generator is calculated to measure the different adjustment performance of critical generators. Then, the excitation system ceiling voltages of critical generators are configured respectively according to the value of sensitivity. The simulation study in the modified 10-machine 39-bus AC/DC hybrid system shows that the transient stability of the system and the transmission power of the area tie-line can be improved significantly with the differential configuration of excitation system ceiling voltages. Under some severe faults, the improvement of the system transient stability is even more significant. This work is supported by Science and Technology Project of State Grid Corporation of China “Technical Research of Grid-Source Coordination Performance Assessment and Optimization based on Generator Performance Differentiation and Power Grid Dominated Stability” and National Natural Science Foundation of China (No. 51577075).